Handle subpatterns from macro expansion

Unfortunately, we can't always offer a machine-applicable suggestion in such cases.

compiler/rustc_mir_build/src/errors.rs

@@ -968,10 +968,12 @@ impl Subdiagnostic for Rust2024IncompatiblePatSugg {
  diag: &mut Diag<'_, G>,
  _f: &F,
  ) {
- diag.multipart_suggestion(
- "desugar the match ergonomics",
- self.suggestion,
- Applicability::MachineApplicable,
- );
+ let applicability =
+ if self.suggestion.iter().all(|(span, _)| span.can_be_used_for_suggestions()) {
+ Applicability::MachineApplicable
+ } else {
+ Applicability::MaybeIncorrect
+ };
+ diag.multipart_suggestion("desugar the match ergonomics", self.suggestion, applicability);
  }
 }

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -340,14 +340,14 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
  && explicit_ba.0 == ByRef::No
  && let ByRef::Yes(mutbl) = mode.0
  {
- // `mut` resets binding mode on edition <= 2021
- assert_eq!(mode.1, Mutability::Not);
-
  let sugg_str = match mutbl {
  Mutability::Not => "ref ",
  Mutability::Mut => "ref mut ",
  };
- s.suggestion.push((pat.span.shrink_to_lo(), sugg_str.to_owned()))
+ s.suggestion.push((
+ pat.span.with_lo(ident.span.lo()).shrink_to_lo(),
+ sugg_str.to_owned(),
+ ))
  }
 
  // A ref x pattern is the same node used for x, and as such it has

tests/ui/pattern/auxiliary/match_ergonomics_2024_macros.rs

@@ -1,11 +1,12 @@
-//@ compile-flags: --edition 2024 -Z unstable-options
+//@ edition: 2024
+//@ compile-flags: -Z unstable-options
 
 // This contains a binding in edition 2024, so if matched with a reference binding mode it will end
 // up with a `mut ref mut` binding mode. We use this to test the migration lint on patterns with
 // mixed editions.
 #[macro_export]
 macro_rules! mixed_edition_pat {
- () => {
- Some(mut _x)
+ ($foo:ident) => {
+ Some(mut $foo)
  };
 }

tests/ui/pattern/match_ergonomics_2024.fixed

@@ -1,8 +1,12 @@
 //@ edition: 2021
 //@ run-rustfix
+//@ rustfix-only-machine-applicable
+//@ aux-build:match_ergonomics_2024_macros.rs
 #![feature(mut_preserve_binding_mode_2024, ref_pat_eat_one_layer_2024)]
 #![allow(incomplete_features, unused)]
-#![forbid(rust_2024_incompatible_pat)]
+#![deny(rust_2024_incompatible_pat)]
+
+extern crate match_ergonomics_2024_macros;
 
 struct Foo(u8);
 
@@ -38,4 +42,16 @@ fn main() {
  let s = Struct { a: 0, b: 0, c: 0 };
  let &Struct { ref a, mut b, ref c } = &s;
  //~^ ERROR: the semantics of this pattern will change in edition 2024
+
+ #[warn(rust_2024_incompatible_pat)]
+ match &(Some(0), Some(0)) {
+ // The two patterns are the same syntactically, but because they're defined in different
+ // editions they don't mean the same thing.
+ (Some(mut _x), match_ergonomics_2024_macros::mixed_edition_pat!(_y)) => {
+ //~^ WARN: the semantics of this pattern will change in edition 2024
+ _x = 4;
+ _y = &7;
+ }
+ _ => {}
+ }
 }

tests/ui/pattern/match_ergonomics_2024.rs

@@ -1,9 +1,10 @@
 //@ edition: 2021
 //@ run-rustfix
+//@ rustfix-only-machine-applicable
 //@ aux-build:match_ergonomics_2024_macros.rs
 #![feature(mut_preserve_binding_mode_2024, ref_pat_eat_one_layer_2024)]
 #![allow(incomplete_features, unused)]
-#![forbid(rust_2024_incompatible_pat)]
+#![deny(rust_2024_incompatible_pat)]
 
 extern crate match_ergonomics_2024_macros;
 
@@ -42,10 +43,15 @@ fn main() {
  let Struct { a, mut b, c } = &s;
  //~^ ERROR: the semantics of this pattern will change in edition 2024
 
+ #[warn(rust_2024_incompatible_pat)]
  match &(Some(0), Some(0)) {
  // The two patterns are the same syntactically, but because they're defined in different
  // editions they don't mean the same thing.
- (Some(mut _x), match_ergonomics_2024_macros::mixed_edition_pat!()) => {}
+ (Some(mut _x), match_ergonomics_2024_macros::mixed_edition_pat!(_y)) => {
+ //~^ WARN: the semantics of this pattern will change in edition 2024
+ _x = 4;
+ _y = &7;
+ }
  _ => {}
  }
 }

tests/ui/pattern/match_ergonomics_2024.stderr

@@ -1,51 +1,51 @@
 error: the semantics of this pattern will change in edition 2024
- --> $DIR/match_ergonomics_2024.rs:10:9
+ --> $DIR/match_ergonomics_2024.rs:14:9
  |
 LL | let Foo(mut a) = &Foo(0);
  | -^^^^^^^^^
  | |
  | help: desugar the match ergonomics: `&`
  |
 note: the lint level is defined here
- --> $DIR/match_ergonomics_2024.rs:5:11
+ --> $DIR/match_ergonomics_2024.rs:7:9
  |
-LL | #![forbid(rust_2024_incompatible_pat)]
- |  ^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | #![deny(rust_2024_incompatible_pat)]
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: the semantics of this pattern will change in edition 2024
- --> $DIR/match_ergonomics_2024.rs:14:9
+ --> $DIR/match_ergonomics_2024.rs:18:9
  |
 LL | let Foo(mut a) = &mut Foo(0);
  | -^^^^^^^^^
  | |
  | help: desugar the match ergonomics: `&mut`
 
 error: the semantics of this pattern will change in edition 2024
- --> $DIR/match_ergonomics_2024.rs:18:12
+ --> $DIR/match_ergonomics_2024.rs:22:12
  |
 LL | if let Some(&_) = &&&&&Some(&0u8) {}
  | -^^^^^^^
  | |
  | help: desugar the match ergonomics: `&&&&&`
 
 error: the semantics of this pattern will change in edition 2024
- --> $DIR/match_ergonomics_2024.rs:21:12
+ --> $DIR/match_ergonomics_2024.rs:25:12
  |
 LL | if let Some(&mut _) = &&&&&Some(&mut 0u8) {}
  | -^^^^^^^^^^^
  | |
  | help: desugar the match ergonomics: `&&&&&`
 
 error: the semantics of this pattern will change in edition 2024
- --> $DIR/match_ergonomics_2024.rs:24:12
+ --> $DIR/match_ergonomics_2024.rs:28:12
  |
 LL | if let Some(&_) = &&&&&mut Some(&0u8) {}
  | -^^^^^^^
  | |
  | help: desugar the match ergonomics: `&&&&&mut`
 
 error: the semantics of this pattern will change in edition 2024
- --> $DIR/match_ergonomics_2024.rs:27:12
+ --> $DIR/match_ergonomics_2024.rs:31:12
  |
 LL | if let Some(&mut Some(Some(_))) = &mut Some(&mut Some(&mut Some(0u8))) {}
  | ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -56,7 +56,7 @@ LL | if let &mut Some(&mut Some(&mut Some(_))) = &mut Some(&mut Some(&mut So
  | ++++ ++++
 
 error: the semantics of this pattern will change in edition 2024
- --> $DIR/match_ergonomics_2024.rs:30:12
+ --> $DIR/match_ergonomics_2024.rs:34:12
  |
 LL | if let Some(&mut Some(Some(_a))) = &mut Some(&mut Some(&mut Some(0u8))) {}
  | ^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -67,7 +67,7 @@ LL | if let &mut Some(&mut Some(&mut Some(ref mut _a))) = &mut Some(&mut Som
  | ++++ ++++ +++++++
 
 error: the semantics of this pattern will change in edition 2024
- --> $DIR/match_ergonomics_2024.rs:39:9
+ --> $DIR/match_ergonomics_2024.rs:43:9
  |
 LL | let Struct { a, mut b, c } = &s;
  | ^^^^^^^^^^^^^^^^^^^^^^
@@ -77,5 +77,21 @@ help: desugar the match ergonomics
 LL | let &Struct { ref a, mut b, ref c } = &s;
  | + +++ +++
 
-error: aborting due to 8 previous errors
+warning: the semantics of this pattern will change in edition 2024
+ --> $DIR/match_ergonomics_2024.rs:50:9
+ |
+LL | (Some(mut _x), match_ergonomics_2024_macros::mixed_edition_pat!(_y)) => {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+note: the lint level is defined here
+ --> $DIR/match_ergonomics_2024.rs:46:12
+ |
+LL | #[warn(rust_2024_incompatible_pat)]
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: desugar the match ergonomics
+ |
+LL | &(Some(mut _x), match_ergonomics_2024_macros::mixed_edition_pat!(ref _y)) => {
+ | + +++
+
+error: aborting due to 8 previous errors; 1 warning emitted